// Impliments the classical cipher "Playfair"
// Usage: cat key.txt message.txt | playfair message -[e/d]
// The decrypted message will be missing spaces and have an x
// in place of every double letter.
//////////////////////////////////////////////////////////////*/

#include<iostream>
#include<vector>
#include<string.h>

using namespace std;

char mat[5][5];
void createMatrix(char key[]);
void prepareText(char origmessage[], char message[]);
void encipher(char message[]);
void decipher(char message[]);

int main(int argc, char** argv)
{
    char message[1000];
    char origmessage[1000];
    char key[25];

    if (argc != 2)
    {
        cout << "Incorrect number of command line arguments, " << endl
            << "Usage: cat key.txt message.txt | playfair message -[e/d] " << endl;
        return false;
    }

    cin >> key;
    cin >> origmessage;

    // function creates the matrix
    createMatrix(key);

    // encipher/decipher flag
    switch (argv[1][1]) {
        case 'e':
            // removes spaces and punctuation, checks for pairs of double letters
            prepareText(origmessage, message);
            // turns plaintext into ciphertext
            encipher(message);
        case 'd':
            // turns ciphertext into plaintext
            decipher(message);
    }

    return 0;
}

void createMatrix(char key[])
{
    int i = 0, j = 0, k = 0;
    int letter = 'a';
    bool ok = true;
    char used[25];

    // keep going until the key runs out
    while(key[k] != '0')
    {
        // we throw out the letter j
        if(key[k] == 'j')
            key[k] = 'i';

        // end of row
        if (j > 4)
        {
            j = 0;
            i++;
        }

        // check to see if the letter is a duplicate
        for(int check = 0; check < k; check++)
        {
            if(used[check]==key[k])
                ok = false;
        }
        // If not a duplicate add it to the matrix
        if(ok)
        {
            cout << mat[i][j];
            mat[i][j] = key[k];
        }
        j++;
        k++;
    }

    // Add remaining letters of the alphabet to the matrix
    for(int remain = k; remain < 25; remain ++)
    {
        // we throw out the letter j
        if(letter == 'j')
            letter++;

        // end of row in matrix
        if (j > 4)
        {
            j = 0;
            i++;
        }

        // check to see if the letter has been used
        for(int check = 0; check < k; check ++)
        {
            if(used[check] == letter)
                ok = false;
        }

        // if letter hasn't been used add it to the matrix
        if(ok)
        {
            mat[i][j] = letter;
            letter++;
        }
    }

    // print out the matrix to test it
    for(int m=0; m < 5; m++)
        for(int n = 0; n < 5; n++)
        {
            cout << mat[m][n] << " ";
        }
}


// remove spaces and punctuation, checks for pairs of double letters
void prepareText(char origmessage[], char message[])
{
    int stepO = 0;
    int stepM = 0;

     //transform(origmessage.begin(), origmessage.end(), origmessage.begin(), ::tolower);

    while(!origmessage[stepO])
    {
        if(origmessage[stepO] >= 'a' && origmessage[stepO] <= 'z')
        {
            if(stepM%2 == 1)
            {
                if(origmessage[stepO] == origmessage[stepO-1])
                {
                    message[stepM] = 'x';
                }
                else
                {
                    message[stepM] = origmessage[stepO];
                    stepO++;
                }

            }
            else
            {
                message[stepM] = origmessage[stepO];
                stepO++;
            }
        }
        stepM++;
    }
}

// this turns our plaintext into cipher text
void encipher(char message[])
{
    int x1, x2, y1, y2, j, k;

    // the first 50 characters of the plaintext
    for(int i =0; i < 50; i++)
    {
        j = 0;
        k = 0;

        // find the 1st character from the message in the matrix
        while(message[i] != mat[j][k] && k < 5)
        {
            j++;
            if(j>4)
            {
                j=0;
                k++;
            }
        }
        x1 = j; // row number
        y1 = k; // column number

        j=0;
        k=0;

        // find the 2nd character from the message in the matrix
        while(message[i+1] == mat[j][k])
        {
            j++;
            if(j>4)
            {
                j=0;
                k++;
            }
        }
        x2 = j; // row number
        y2 = k; // column number

        // if they are not in the same row or column
        if(x1!=x2 && y1!=y2)
        {
            message[i] = mat[x1][y2];
            message[i+1] = mat[x2][y1];
        }

        // if they in the same row
        else if(y1 != y2)
        {
            if(x1 == 4)
                message[i] = mat[0][y1];
            else
                message[i] = mat[x1+1][y1];
            if(x2 == 4)
                message[i+1] = mat[0][y2];
            else
                message[i+1] = mat[x2+1][y2];
        }
        // if they are in the same column
        else
        {
            if(y1 == 4)
                message[i] = mat[x1][0];
            else
                message[i] = mat[x1][y1+1];
            if(y2 == 4)
                message[i+1] = mat[x2][0];
            else
                message[i+1] = mat[x2][y2+1];
        }
        i++;
    }
}
void decipher(char message[])
{
    int x1, x2, y1, y2, j, k;

    // the first 50 characters of the plaintext
    for(int i =0; i < 50; i++)
    {

        j = 0;
        k = 0;

        // find the 1st character from the message in the matrix
        while(message[i] != mat[j][k] && k < 5)
        {
            j++;
            if(j>4)
            {
                j=0;
                k++;
            }
        }
        x1 = j; // row number
        y1 = k; // column number

        j=0;
        k=0;

        // find the 2nd character from the message in the matrix
        while(message[i+1] == mat[j][k])
        {
            j++;
            if(j>4)
            {
                j=0;
                k++;
            }
        }
        x2 = j; // row number
        y2 = k; // column number

        // if they are not in the same row or column
        if(x1!=x2 && y1!=y2)
        {
            message[i] = mat[x1][y2];
            message[i+1] = mat[x2][y1];
        }

        // if they in the same row
        else if(y1 != y2)
        {
            if(x1 == 0)
                message[i] = mat[4][y1];
            else
                message[i] = mat[x1-1][y1];
            if(x2 == 0)
                message[i+1] = mat[4][y2];
            else
                message[i+1] = mat[x2-1][y2];
        }
        // if they are in the same column
        else
        {
            if(y1 == 0)
                message[i] = mat[x1][4];
            else
                message[i] = mat[x1][y1-1];
            if(y2 == 0)
                message[i+1] = mat[x2][4];
            else
                message[i+1] = mat[x2][y2-1];
        }
        i++;
    }
}